1. Field of the Invention
The present invention relates to a control for suppressing power consumption in a recording apparatus that uses a spectrum spread function in clock generation means.
2. Description of the Related Art
In conventional recording apparatuses (printers), in order to cope with improvements in image quality, and increases in image recording speeds, a complicated control circuit is required, and the operational speed of such control circuits is increasing. As a result, the frequency of a clock signal supplied to the control circuit also increases, and, among other consequences, the level of EMI (electromagnetic interference) noise radiated from an ASIC (application specific integrated circuit) having a large circuit scale is becoming high.
In order to deal with the aforesaid problems associated with increased clock signal frequency, a semiconductor device called a spectrum spread clock generator (abbreviated as an “SSCG”) has been used. In spectrum spreading, the frequency of a clock signal, which fixed frequency obtained from a frequency oscillator, such as a quartz oscillator or the like, is periodically changed. By performing spectrum spreading in a spectrum spread clock generator, the generation of EMI noise can be suppressed by spreading the frequency for generating EMI noise from a circuit.
Recently, energy saving in printers is being requested, and, in response, a CPU (central processing unit) is typically provided in a control circuit waiting in an energy saving mode when a printing apparatus is in a standby state in which a recording operation is not performed. In one approach, to perform recording operation, a printer shifts from the energy saving mode to a normal or operation mode by performing a key operation on an operation panel provided in a recording apparatus. In another approach, such a shift from the energy saving mode to the normal or operation mode can be performed by an instruction from software (a printer driver or the like) operating in a host computer or the like. Further, some apparatuses have an automatic power-off function, by which they shift to an energy saving mode when a predetermined time period has elapsed after a recording operation.
In spectrum spread clock generators, however, although the generation of EMI noise can be suppressed, power consumption is relatively large compared with other semiconductor devices, resulting in an increase in power consumption in a circuit using a spectrum spread clock generator. Such an increase in power consumption causes a problem in an apparatus including a spectrum spread clock generator, such as a printer or the like, when, for example, it is intended to set power consumption in a standby state to a value equal to or less than 0.1 W.